Virulence of Bacteroides nodosus in ovine footrot

L. J. Depiazzi

Virulence, in relation to ovine footrot, was examined in a review which emphasised the primary role of Bacteroides nodosus, an anaerobic strict parasite of ungulates. The association of this parasite with other bacteria in the footrot lesion resulted in complex interactions of host. parasite and environment. However, experimentation showed that the severity of the footrot lesion was associated principally with two different properties of B. nodosus: protease stability and surface translocation, the latter being a probable function of the pilus. The relationship between virulence, extracellular protease and translocation was elucidated in terms of function rather than structure. For example, the severity of footrot lesions was not related specifically to the electrophoretic mobility of protease isoenzymes or outer membrane proteins of B. nodosus. Although there were only two levels of protease stability, surface translocation, measured as either colony size or degree of cellular twitching, varied continuously between isolates. It was suggested that surface translocation was the basis for a continuous spectrum of virulence observed in ovine footrot. Nevertheless, protease stability was associated specifically with microbial penetration of the epidermal matrix of the hoof , hence justifying a classification of B. nodosus isolates into virulent (stable protease) and benign (unstable protease) strains. Although this classification was considered realistic, the complexity of ovine footrot was emphasised by evidence that twitching motility mediated the effects of both ambient temperature and the footrot microbial flora on the severity of all forms of the disease.

Virulence of Bacteroides nodosus in ovine footrot

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